Purity - Sewon cancels all harmful magic upon himself and allies around him with Kubera's power
Cycle of Death and Rebirth - Sewon exchanges his HP with a target. He gets more of the enemy's HP while giving away only half of his HP unless the enemy escapes from the AOE in a certain time.

Along with Ridika, Sewon initially did not have a voice when he was first introduced.

During the beta of Archeblade, Sewon's space + R initially had recoil, making Sewon move backwards when he used the attack. The recoil was later removed to make Sewon easier to use as a rush-down character.

Sewon initially didn't get super armor when he used his "Cycle of Death and Rebirth" skill. This left him susceptible to attacks during the animation and after it took effect. Later, he was given super armor when he used the skill to give him more survivability, allowing him to kill off weakened opponents without having to worry about hitstun.

These changes, along with a few minor tweaks, allowed players to use Sewon more offensively in the final release.

Sometime after the official release, players found a glitch that allowed Sewon to move while using his R skill. This glitch was never fixed.